Many known thermoelectric devices utilize the Peltier effect for heating or cooling. Typically, a direct current is provided across a semiconductor material and/or across an array of interconnected semiconductor materials of different types (e.g., semiconductor materials having different doping properties). As a result of the current, the junction either generates heat or rejects heat (cooling). The heating or cooling effect of thermoelectric devices is used in a number of contexts ranging from superconductivity to microprocessor cooling devices to electric beverage coolers.
The Figure of Merit (FOM) describing the performance of typical thermoelectric devices is given by Equation (1) below:Z=Se2ke/kT  (1)In Equation (1), Z is the FOM; Se is the Seebeck coefficient of the device; ke is the electrical conductivity of the device and kT is the thermal conductivity. It can be seen that the performance of thermoelectric devices (Z) is proportional to electrical conductivity and inversely proportional to thermal conductivity. In other words, high electrical conductivity of the device material improves performance, while high thermal conductivity of the device material degrades performance. Accordingly, the ideal material for thermoelectric devices would be one that has a high electrical conductivity and a low thermal conductivity. Unfortunately, for most practical materials, electrical and thermal conductivity are proportional. As a result, existing thermoelectric devices suffer performance degradation due either to an excess of thermal conductivity or a lack of electrical conductivity.